Because Windows system design is ages better than any Unix, except for Solaris, maybe. That would then be a downgrade.

Ha, you really made me laugh? Windows system design being better than the Unix approach? Have you ever actually looked at the Linux approach?

One question: Can you install a new version of Windows over an existing version of Windows while you're working on that machine at the same time? Just one example of things you can do with Linux which you can't do on Windows.